Undemanding synthesis of N,P co-doped carbon nanosheets for the hydrogen evolution reaction: combining experimental quantitative analysis and DFT calculation corroboration

Abstract

Developing a cost-effective catalyst for the hydrogen evolution reaction (HER) is of foremost importance for a new energy layout and has broad development prospects. Metal-free heteroatom-doped carbon materials have emerged as a focal point of research due to their low price, superior electrical conductivity, and exceptional corrosion resistance. However, there is a paucity of detailed examinations into the distinct mechanisms of HER activity enhancement of different forms of heteroatomic species on HER activity. To maximize the potential of metal-free heteroatom-doped carbon materials for the HER, the respective doping effect on the catalytic activity should be elucidated. Herein, we developed a one-step pyrolysis to synthesize N and P co-doped carbon nanosheets. Chain-structured amino acids are cross-linked with phytic acid to form a huge nanocarbon network that lies flat in two dimensions. The prepared catalyst exhibits an active surface area of 93.5 mF cm⁻² and the thickness of the nanoplates was less than 10 nm. The ultra-large active surface area provides the basis for an efficient HER. By changing the feeding ratios of precursors, the proportions of different fractions of N species and P species showed certain trends. By constructing different double-doping models, the changes in the electron cloud density at the double-doped sites within the local π bonds were related to the changing trends of hydrogen adsorption free energy. Experimental and theoretical analyses indicate that under the electronic perturbation of graphitic N and C₃PO, the surrounding carbon atoms undergo charge polarization, and their ΔG_H* is optimized after electron rearrangement, which promotes the HER process.